Dialdehyde polysaccharide-polyacrylamide compositions



United States Patent 3,117,949 DIALDEHYDE POLYSACCHARIDE-POLYACRYL-AMIDE COMPOSITIONS Peter J. Borchert, Eikhart, ind, assignor to MilesLaboratories, Inc., Elkhart, 11111., a corporation of Indiana N0Drawing. Fiied July 7, 1960, Ser. No. 41,225 Claims. (Cl. 260-73) Thisinvention relates to polymer compositions derived from polymers ofacrylamide and dialdehyde polysaccharides. In one of its more particularaspects this invention relates to films formed from the interaction ofpolymers of acrylamide and dialdehyde polysaccharides.

The reaction between dialdehyde starch and monomeric acrylamide iscovered in my copending application, U.S. Serial No. 27,263, filed May6, 1960.

Polyacrylamide and its copolymers in the form of aqueous dispersions areused extensively in the preparation of films having a wide variety ofindustrial applications such as binders for cellulosic fibers, coatingsfor paper, pigment retention improvers in paper, thickening agents inwater base paints and highly effective fiocculants among others. Many ofthe aforementioned uses require films with highly effective waterresistance.

It is a well known fact that plastic films formed from aqueousdispersions of polyacrylamide and some of its Copolymers have a tendencyto swell, soften and re-disperse upon contact with water. Completedestruction of the fihn takes place within a relatively short period oftime depending upon such factors as film thickness, drying conditionsand immersion temperature. For many of the uses to which dispersions ofthese polymers are put a more effective water and scrub resistance and ashorter film drying time is desirable.

Virtual insolubilization of polyacrylamides can be attained in acondensation reaction involving the amide groups of the repeatingpolymeric units, wherein the polyacrylamide dispersions are treated withlarge amounts of strong acids, for example, 50 parts by weight of 48%hydrobromic acid to parts dry weight of acrylamide dispersed in waterand heated at 90100 C. for several hours. The result is intraandintermolecular imidization which tends to reduce water solubility.

A number of substances are capable of undergoing condensation reactionswith polyacrylamide and its copolymers to yield water-insensitive films.Some of the operable substances in this instance are urea-formaldehyderesins, melamine-formaldehyde resins, polybasic acids, and the like. Ineach case high temperatures and relatively large amounts of an acidiccatalyst are required to eiiect the reactions.

Another group of agents which can be used to insolubilize thepolyacrylamide dispersions are the dialdehydes, such as glyoxal. A primedisadvantage in using glyoxal, however, especially at temperatures of 65C. or higher is an undesirable color formation in the films. An addeddisadvantage is that relatively large amounts of glyoxal are requiredfor insolubilization.

It is accordingly a principal object of this invention to providepolymeric compositions which have the desirable properties ofpolyacrylamide film-formers and in which the undesirable properties ofthese polymers are not present.

Another object of this invention is to provide compositions which may beused to form films having improved water resistance.

Another object of this invention is to provide films of superiordurability.

3,117,949 Patented Jan. 14, 1964 A further object of this invention isto provide a method for the preparation of compositions having theaforesaid desirable properties.

Other objects and advantages of this invention will become apparent inthe course of the following detailed disclosure and description.

It has now been found that compositions having the already desirableproperties of polymers of acrylamide and improved properties withrespect to water resistance and durability may be prepared by theinteraction of polymers of acrylamide with dialdehyde polysaccharides inthe presence of strong acidic catalysts. The resulting compositions arecharacterized by forming films which are clear and stable not only uponcontact with water but even under more severe solvent treatment.

The acrylamide polymers which may be used in the novel compositions ofthis invention may be homopolymers of acrylamide or copolymers preparedby the copolymerization of acrylamide with various comonomerscopolymerizable therewith.

Comonomers which can be used in the practice of this invention includemethacrylamide, N-methylolacrylamide, acrylic acid, methacrylic acid,butadienes, acrylo nitrile, acrylylurea, butyl methacrylate, ethylacrylate, methyl acrylate, butyl vinyl ether, diallyl cyanamide, methylvinyl ketone, styrene, unsaturated alkyds, vinyl acetate, vinylchloride, vinyl ethers, vinyl ketones, vinyl pyridines,Nvinylpyrrolidone, N-allylacetoacetamide and others of like nature.Copolymers resulting from the copolymerization of acrylamide withmixtures of the above compounds, such as with acrylonitrile and ethylacrylate, acrylonitrile and methyl acrylate, acrylonitrile and N-methylacrylamide, N allylacetoacetamide and vinyl acetate,2-vinylpyridine and methacrylic acid, and other combinations may also beused.

For the sake of convenience, both polyacrylamide itself and acrylamidecopolymers will hereinafter be referred to as polyacrylamides.

The polyacrylamides are preferably used as aqueous dispersions which maybe made up as required. They are available as powders which may bedispersed in water to form the desired aqueous dispersions.

The dialdehyde polysaccharides which interact with the polyacrylamidesto form the novel compositions of this invention are those obtained bythe oxidation of polymeric polysaccharides such as by the action ofperiodic acid. This well known reaction may be exemplified by theoxidation of starches with periodic acid in accordance with the equationshown below:

$32011 onion 1 1 H104 If 0 OH H I l on no Q H OH II [I J where nrepresents the number of repeating units in the starch molecule. It maybe seen that the resulting prodnot of this oxidation, known in the artas dialdehyde starch, is a polymer which contains two aldehyde groupsper glycoside unit of the starch molecule resulting from oxidation ofthe corresponding 1,2-glycol. Other polysaccharides than starches may beutilized in the preparation of the polymeric dialdehydes, for example,celluloses, dextrins, dextrans, inulins and the like. It will beappreciated that dialdehyde starch and other dialdehyde polysaccharidesmay exist with varying degrees of oxidation depending upon theconditions under which the 3 oxidation reaction is carried out. For thepurpose of this invention, in order to prepare films having the greatestdegree of Water insensitivity, it is preferred that a highly oxidizeddialdehyde starch be used, for example, one comd hyde polysaccharides onthe other. The exact mechanism of the cross-linking reaction is notknown but it is likely that interaction between the two types ofpolymers results in the formation of cross-linkages between the prisinga starch which has been about 90% oxidized. By 5 amide groups of theacrylamide fractions and the aldea 90% oxidized starch is meant one inwhich 90 out of hyde groups of the repeating units of the dialdehydepolyevery 100 glycoside units have been converted to the disaccharidegiving rise to a relatively stable polymeric comaldehyde. Other levelsof oxidation may, of course, be position which may be characterized ashaving the folutilized if desired. lowing structure:

Ealdehyde starch may be advantageously prepared for use in the form ofan aqueous dispersion by heating an V J aqueous slurry of the dialdehydestarch until a homogene- 6:0 ous dispersion of dialdehyde starch isobtained, for ex- J; ample by heating in water at a temperature of about70 C. Heating with a 0.1 N to 1.0 N solution of a buffer (IJZO salt suchas sodium acetate, sodium bicarbonate, disodi- 0 NH urn phosphate or thelike, at a temperature of 40 C. to l 50 C. aids the stability of thedialdehyde starch and is I l especially effective for this purpose.'Dialdehyde starch T dispersions may be prepared in any desiredconcentration. CHE-OH X For most purposes, however, a concentration offrom about 5% to about is preferred. Dispersions of wherein x representsthe number of repeating units in the other dialdehyde polysaccharidesmay be similarly premolecule. pared. Such dispersions may then beutilized for pre- This intermolecular cross-linkage formation is foundto paring the novel compositions of this invention without 25 occur upondrying of the water by evaporation at room further treatment. If thepolyacrylamide is to be used temperatures or elevated temperatures. Ithas been obas a dispersible powder then the dialdehyde polysacchaservedthat only a slight amount of cross-linkage between ride may also be usedin this form. the two polymeric chains is required for insolubilization.

In the practice of the present invention the dialdehyde This effect, ofcourse, gives the films excellent water restarch or other dialdehydepolysaccharide may be used 818 1 a Well as Other desirable P p in anamount f from about 005 10 about 2% based The invention will be betterunderstood by reference on the weight of the polyacrylamide andpreferably in the to the following eXamples which are included for Prange of from about 0.5% to about 1%. It is notable poses ofillustration and are not to be construed as in any that in practiceabout 50-100% less dialdehyde polysac- Way limiting the scope of theinstant invention. charide is required than glyoxal for insolubilizationof polyacrylamides. EXAMPLE I The Pf p Of these novel lwlymefiCCompositions A 2.8% dispersion of polyacrylamide was prepared by havingP Water resistanch i5 P y y flccom heating 2.8 g. of polyacrylamideunder stirring with 97 g. Phshfid y mixing a dispersion of thePolyacrylamide with water at 80-90 C. for 2 hours and then cooled toroom a dispersion of the dialdehyde polysaccharide in theprestgmperature @1106 Of a Strong acidic Catalyst at a y ion 10 g. of90% oxidized dialdehyde starch and 90 g. of Centratioh of from ahmlt P 2to P The dialdfihyde tap water were heated for 15 minutes under stirringat 70 polysaccharide dispersion y he P p for use C., giving a 10%dispersion or" dialdehyde starch. scribed above- The Polyacrylfimide yhe Similarly P Amounts of 0.5 and 1.0% of the dialdehyde starch pared yheating Said PP P y in Water, dispersion (dry basis) were added to thedispersion of but in general SOI'IIeWhZI't higher temperatures,eXflmpolyacrylamide at room temperature and the pH adjusted P P about 10are q If dashed, to 5 with acetic acid, to 2 with phosphoric acid, to 2the dlaldehyde polysaccharide y he added to the P 3 with hydrochloricacid and to 5 with zinc chloride. After acrylamide at a highertemperature than room temperamixing th i gredie t fil were t d were eithture, but elevated temperatures are not essential for this d i d f 2 hot C, f ll i an ddi i l purpose. In fact, room temperature is preferredsince less ing t 27 (3., o fo 16 hours at 27 C, Strips e t degradationof the polymers occurs at room temperature from the fil nd immersed inwate at 25 C, f 2 than at elevated temperatures. ho

As catalyst may be used any strong acid. Particularly The results aresummarized in Table I below. Very effective are hydrochloric acid andphosphoric acid. 59 good results have been obtained with as little as0.5% di- Other acids which may be used include acetic acid,hydroaldehyde starch in the presence of strong acidic catalysts bromicacid, and salts,'such as zinc chloride. 7 (phosphoric and hydrochloricacid at a pH of 2).. Film The formation of the novel polymericcompositions of strips of Experiments 3 and 4 were found to be unchangedthis invention and the improved water resistance thereof and not stickyunder the conditions described herein, is believed to be due to across-linking reaction between 99 while strips from Experiments 1, 2 and5 dissolved withthe chains of polyacrylarnides on the one hand anddialdein 10 minutes.

' Table I Dialdehyde I Observations upon immersion at 25 C. for 2 hrs.

Exp. Catalyst pH N0. (dry Oven dried 2 hrs. at, 65 C.

basis) following 12 hours drying Dried at 27 C. for 16 hours. I at 27 C.

1 Acetic acid 5 Dissolves within 10 min Dissolvcs within 10 min. 2 1.0do 5 Film intact, but soft and D0. 3 0.5 Phosphoric acid.-. 2 iii taet,somewhat soft, Film intact not sticky.

. not sticky. 4 0.5 Hydrochloric acid... 2 do Do. 5 0.5 Zinc chloride 5d0 Dissolves within 10 min.

The following example illustrates the preparation of the compositions ofthis invention using a copolymer of acrylamide.

EXAMPLE II polymer of acrylamide and said dialdehyde polysaccharidebeing reacted in the form of aqueous dispersions thereof, saiddialdehyde polysaccharide being a highly oxidized dialdehydepolysaccharide and being used in an amount of about from 0.05% to about2% based on the AH 83% dispersion of a copolymer of acrylamide and 5weight of the polymer of acrylamide, said reaction being acrylic acidwas P p by'lheating 80 Of the conducted at a hydrogen ion concentrationof about from polymer with stirring at 80 C. with 920 g. of water untilH 2 t H 5, solution took place. 2. A composition according to claim 1wherein the A dispersion of dialdehyde Starch was P p catalyst is amember selected from the group consisting as described in Example No. I.Amounts of 0.5%, 10 of hydrochloric acid and phosphoric acid.

1.0% and 2.0% Of the dialdehyde starch dispersion (dry 3 A compositionaccording to claim 1 wherein the basis) were combined with thedispersion of the p ypolymer of acrylamide is a homopolymer ofacrylamide. mer of acrylamide and acrylic acid at room tempera- 4, Acomposition according to lai 1 wherein the T n phosphoric acid (based011 y weight polymer of acrylamide is a copolymer acrylamide with 0f p ywas added to P After miXing, t a comonorner copolymerizable therewith.

solutions were cast on glass plates at 65 C. for 4 hours, 5, Acomposition according to claim 1 wherein the diyielding films of from5-8 mils thickness. Strips were aldehyde polysaccharide is dialdehydestarch.

cut from the films and immersed in water at 27 C. and 6. A compositionaccording to claim 1 wherein the at 100 C. polymer of acrylamide is acopolymer of acrylamide and The results are shown in Table II,following. The acrylic acid. blank dissolved in water at roomtemperature in 6 min- 7. A film formed upon drying of an aqueous dispeutes (experiment 6), while films containing 1% and 2% sion of theproduct of claim 1. dialdehyde starch remained in perfect condition forone 8. A process for the preparation of a water insensihour and longerafter immersion at 27 C. (experiments tive polymeric composition whichcomprises reacting a 8 and 9), except that swelling had occurred. At thepolymer of acrylamide with a dialdehyde polysaccharide temperature ofboiling water the blank dissolved immediin the presence of a strong acidcatalyst, said polymer ately upon immersion (experiment 6), while filmsmade of acrylamide and said dialdehyde polysaccharide being from theaddition of 1% and 2% dialdehyde starch rereacted in the form of aqueousdispersions thereof, said mained intact for 15 minutes and longer(experiments dialdehyde polysaccharide being a highly oxidized di- 8 and9). aldehyde polysaccharide and being used in an amount of Table IIDialtlehyde Dialdehyde Obscrvati0nsFil1ns cured for 4hrs. at 65 C. andimmersed Exp. Copolymer, starch starch, in water at N 0. g. solution,percent g. by wt.

6 5O Dissolvcsinfimin Went immediately into solu- 7 0.39 0.5 Filmperfect for 30min Fi lha dissolved completely in S 50 0.78 1.0 Filmperfect for 1 hr. and Fi lrfi htact for 15 min. and

longer. longer. 9 50 1.56 2.0 Film perfect for 1 hr. and Film intact for15 min. and

longer. longer.

1 Catalyst-phosphoric acid, 10% by weight. 2 5% by weight in tap water.

It can thus be seen that the use of dialdehyde polysaccharides withpolyacryamides results in films which do not re-disperse upon immersionin water even at elevated temperatures. On the other hand, films formedfrom polyacrylamides alone are seen to re-disperse in water within avery short period of time and usually Within a few minutes. The novelcompositions of this invention, then, have been shown to have enhancedwater resistance and improved stability and films formed from thesecompositions have been shown to be considerably more durable than filmsformed from polyacrylamides themselves.

In summary, this invention provides polymeric compositions formed fromthe interaction of polyacrylamides and dialdehyde polysaccharides in thepresence of strong acidic catalysts. These compositions are capable offorming films of greatly improved water resistance and durability.

Other embodiments than those specifically described may, of course, beused in the practice of this invention and are intended to be includedwithin the scope thereof, which is defined in the appended claims.

What is claimed is:

1. A composition comprising a product obtained by reacting a polymer ofacrylamide with a dialdehyde polysaccharide in the presence of a strongacid catalyst, said about from 0.05% to about 2% based on the weight ofthe polymer of acrylamide, said reaction being conducted at a hydrogenion concentration of about from pH 2 to pH 5.

9. A process according to claim 8 wherein the catalyst is a memberselected from the group consisting of hydrochloric acid and phosphoricacid.

10. A process according to claim 8 wherein the polymer of acrylamide isa homopolymer of acrylamide.

11. A process according to claim 8 wherein the polymer of acrylamide isa copolymer of acrylamide with a comonomer copolymerizable therewith.

12. A process according to claim 8 wherein the dialdehyde polysaccharideis dialdehyde starch.

13. A process according to claim 8 wherein the polymer of acrylamide isa copolymer of acrylamide and acrylic acid.

14. A process according to claim 8 wherein the aqueous dispersion of thedialdehyde polysaccharide is prepared by heating an aqueous slurry ofsaid dialdehyde polysaccharide with a 0.1 N to 1.0 N solution of abuffer salt at a temperature of about from 40 C. to 50 C.

15. A process for the preparation of a water insensitive film whichcomprises reacting a polymer of acrylamide with a dialdehydepolysaccharide in the presence of a strong acid catalyst, said polymerof acrylamide .and said dialdehyde polysaccharide being reacted in theform of aqueous dispersions thereof, said dialdehyde polysaccharidebeing a highly oxidized dialdehyde polysaccharide and being used in anamount of about from 0.05% to about 2% based on the weight of thepolymer of acrylarnide, said reaction being conducted at a hydrogen ionconcentration of about from pHZ to pHS and drying the resulting aqueousdispersion to form a film.

References flirted in the file of this patent UNITED STATES PATENTSBarry et a1. May 5, I959 Woodberry et a1. June 16, 1959 Hofreiter eta1.: TAPPI 43, 63943, 1960.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,11%949 January 14 1964 Peter J, Borchert It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 2 lines 49 to 54 the equation should appear as shown belowinstead of as in the patent:

ca oa cu oa H10 OH H 0-- CH HC H OH H H (SEAL) Attest:

ERNEST Wa SWIDER EDWARD JO BRENNER Attesting Officer Commissioner ofPatents

1. A COMPOSITION COMPRISING A PRODUCT OBTAINED BY REACTING A POLYMER OFACRYLAMIDE WITH A DIALDEHYDE POLYSACCHARIDE IN THE PRESENCE OF A STRONGACID CATALYST, SAID POLYMER OF ACRYLAMIDE AND SAID DIALDEHYDEPOLYSACCHARIDE BEING REACTED IN THE FORM OF AQUEOUS DISPERSIONS THEREOF,SAID DIALDEHYDE POLYSACCHARIDE BEING A HIGHLY OXIDIZED DIALDEHYDEPOLYSACCHARIDE AND BEING USED IN AN AMOUNT OF ABOUT FROM 0.05% TO ABOUT2% BASED ON THE WEIGHT OF THE POLYMER OF ACRYLAMIDE, SAID REACTION BEINGCONDUCTED AT A HYDROGEN ION CONCENTRATION OF ABOUT FROM PH 2 TO PH 5.